where

Return a copy of this descriptor requiring affinity at its execution site — the producer-side eligibility tagging step, the sibling of TaskDescriptor.inLane(...). Everything else (op, args, trace, pin, lane) is preserved, so eligibility composes with a lane. This is the shipped .where { } surface: build a TaskDescriptor, tag it with where, and enqueue it on a WarpNode. Placement then hashes over the eligible subset.